1. Field of the Invention
The present invention relates to sucker rod pumps and more particularly to long stroke sucker rod pumps and sucker rod pumps in deviated petroleum wells.
2. Description of Prior Art
Pumping petroleum, water and other minerals with sucker rods and sucker rod pumps is an old and well used method of extraction of liquid minerals from the earth. In the past, most sucker rod pumped wells were almost vertical or would deviate from vertical by no more than eight degrees or ten degrees. With this relatively minor deviation in the well there is little or no torque caused by sucker rods rubbing and twisting inside of the tubing and therefore this problem was not addressed to any great extent. If the problem did exist, there would be a swivel added to the carrier bar of the pumping unit, or the two wire lines on the horsehead would be sufficient to counter any torque that may exist.
There are two recent changes in the art of petroleum pumping that now are causing greater torque to be placed on the sucker rod string. One change has been with the increased use of long stroke pumping devices that have sucker rod strokes ranging from fifteen feet to one hundred feet. The other change has been the addition of rod guides to sucker rod strings allowing sucker rods to be placed in wells with deviation of over ninety degrees; often these highly deviated wells look like cork screws when shown in plan view.
When pumping petroleum from these highly deviated wells the sucker rods will twist and turn causing torque on the rod string. Some of the torque is relieved in the downhole pump, with the rest of the torque being relieved in a swivel on the carrier bar of the surface pump. Often on long stroke pumps the torque is allowed to twist a single cable which could cause the individual strands or wires that make up the cable to rub or chafe and then break down. One long stroke pumping unit that has a single cable running into the well is the GAULT unit with a U.S. Pat. No. 4,062,640, issued on Dec. 13, 1977 .
Other long stroke pumps use chains rather than cables and arrests the torque with roller guides. The problem with the method of arresting torque with roller guides is that the chain will twist below the roller guides thus causing the chain to wear out more rapidly due to the twist in the chain and the greater wear on one side as the chain passes over the roller guides. If the mechanical chain is put into any torque it will wear out more rapidly.
There are two pumping devices that guide the mechanical chain with roller guides as noted: they are James, with a patent issued on Apr. 15, 1980, U.S. Pat. No. 4,197,766 and Chardonneau et al, with a patent issued on Dec. 20, 1977, U.S. Pat. No. 4,063,827. These devices teach the resistance of torque on a sucker rod string after the torque reaches the cable chain or polished rod thus causing more wear and stress on the chain.